I bought the five volume, slipcased German complete collection of Gaston last year, so I don't know what is available in French atm.
As to the info on Integrales, I just do what I (many others here) do with US books: 'fishing' on Amazon. I search for "Integrale, Dupuis" on Amazon.fr and order them by date of publication.
I think that's the one:
https://www.amazon.com/Locke-Key-Sma...=locke+%26+key